51661581 has 4 divisors (see below), whose sum is σ = 68882112. Its totient is φ = 34441052.

The previous prime is 51661537. The next prime is 51661609. The reversal of 51661581 is 18516615.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 51661581 - 2²⁵ = 18107149 is a prime.

It is a super-2 number, since 2×51661581² = 5337837902839122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51661501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8610261 + ... + 8610266.

It is an arithmetic number, because the mean of its divisors is an integer number (17220528).

Almost surely, 2^51661581 is an apocalyptic number.

It is an amenable number.

51661581 is a deficient number, since it is larger than the sum of its proper divisors (17220531).

51661581 is a wasteful number, since it uses less digits than its factorization.

51661581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17220530.

The product of its digits is 7200, while the sum is 33.

The square root of 51661581 is about 7187.5991123601. The cubic root of 51661581 is about 372.4396394847.

The spelling of 51661581 in words is "fifty-one million, six hundred sixty-one thousand, five hundred eighty-one".